Several different types of random-access memory (RAM) exist and are suitable for different purposes. Dynamic random-access memory (DRAM) is a type of RAM that stores each bit of data in a separate capacitor using a corresponding transistor. The capacitor can be either charged or discharged, and these two capacitor states may represent logical high or low values, respectively. Because the capacitors will slowly discharge in current implementations due to transistor leakage, the capacitor charge is refreshed periodically, which leads to the term “dynamic” in the name DRAM. DRAM is a volatile memory since data stored in the capacitors is lost quickly when power is removed and is widely used as the main memory in modern computers.
One type of DRAM is referred to as synchronous dynamic random-access memory (SDRAM). SDRAM has a synchronous interface coordinated by an externally supplied clock signal. SDRAM may be divided into several independent sections of memory referred to as “banks,” allowing an SDRAM to operate on several memory access commands concurrently, provided the commands are independent of each other (e.g., interleaved). This division into banks allows SDRAMs to achieve more concurrency and higher data rates than asynchronous DRAMs.